Various types of exhaust gas composition sensors are known; in one structure, a plate-like element is retained in a housing which is in the form of a plug capable of being screwed into a component of the exhaust system of an internal combustion (IC) engine. The actual sensing element, usually, is a structure, for example in plate form, of zirconium dioxide, which may be self-supporting or applied to a carrier substrate, for example in plate form, and which is seated in the plug. Difficulties arise in connection with holding and sealing the sensed element within the plug.
U.S. Pat. No. 4,283,261 MAURER et al, describes a gas sensor which has a sealing structure in which two matching elements, which surround the carrier, are arranged to form a pocket or chamber. The pocket or chamber is filled with a sealing material, such as glass, a cement, a hardenable putty, or the like. The glass or the cement, respectively, fills the pocket, but does not seal the region between the respective structural elements and the metal housing. It has been found that, over extended operating times, and particularly when being subjected to vibration, cement, or glass, or other rigid hardenable substances are not satisfactory for long, trouble-free operating life.
Another type of structure is disclosed in German Patent Disclosure Document No. DE-OS 26 57 541, which describes a gas sensor having a plate-like carrier positioned in a metal housing and retained therein by mean of a ceramic cement. The ceramic cement, which also forms a seal, has low resistance to vibration. Additionally, it is difficult to handle such a ceramic cement under mass production conditions. Ceramic cement is also described in U.S. Pat. No. 4,007,435, Tien; it may, for example be formed of a composition of a ceramic powder such as MgO, and sodium silicate, or a binder, such as phosphate.
U.S. Pat. No. 4,334,978, MULLER et al, assigned to the assignee of the present application, describes a sealing arrangement in which a plate-like carrier is guided through a slit formed in a metal disk secured in a metal housing. The plate-like carrier is secured behind the disk by a glass melt or by hard solder. The melt or the solder simultaneously seals the gap between the metal disk and the metal housing, as well as retaining the plate-like carrier therein. Such a seal is eminently suitable, but difficult to make economically under mass production conditions with low reject rate and high utility, and particularly when subjected to vibration or shock.
Gas sensors which have a plate-like carrier, possibly including heater elements thereon, and constructed, for example, in layer arrangement, are known in various embodiments and constructions. Examples of gas sensors with heat elements are also contained and shown in the foregoing literature references.
Electrical connection of sensor elements and heater elements are described in the foregoing references and, further, in German Patent Disclosure Document Nos. DE-OS 26 57 541 and DE-OS 25 48 019, as well as in U.S. Pat. No. 4,007,435, which show show solder connections. U.S. Pat. No. 4,157,282 describes a rivet connection for a layer-like sensor element; German Patent Disclosure Document No. DE-OS 31 50 435 discloses a plate-like carrier having depressions or through-bores formed therein through which a connecting wire can be placed, and retained by a sinterable retaining mass, for example a noble metal cermet. German Patent Disclosure Document No. DE-OS 25 26 340 shows an arrangement in which a clamping connection is referred to in the specification, although no such connection is shown in the drawing.